This invention relates to a cartridge filter with the use of a microporous filter membrane. More particularly, it relates to a cartridge filter with the use of a hydrophilic microporous filter membrane having a high chemical resistance which is appropriately usable in processes for producing, for example, semiconductors and drugs.
In the production of semiconductors, there have been recently required filters which are highly resistant to liquid chemical agents such as organic solvents, acids, alkalis and oxidizing agents and provide little eluate. It is a present-day practice to use, in filtering these liquid chemical agents, filters consisting of microporous microfilter membranes made of polytetrafluoroethylene (PTFE) and other filter-constituting members made of fluoropolymers.
However, PTFE filter membranes suffer from a problem that since they have a highly hydrophobic nature, they would undergo air-rock even upon contamination with only a very small amount of bubbles thereby making filtration impossible, even though they have been moistened with isopropanol at the initiation of the filtration. When these fluoropolymer filters are disposed after using, there arises another problem that toxic gases are generated by incineration.
Under these circumstances, an object of the invention is to provide a filter cartridge which withstands the filtration of acids, alkalis, oxidizing agents, alcohols, in particular, a liquid mixture of hydrochloric acid with an aqueous solution of hydrogen peroxide (i.e., so-called HPM) and isopropanol at a high temperature (60 to 80xc2x0 C.), as frequently used in processes of producing semiconductors and drugs, and the filters of which can be easily disposed by incineration after using.
The object of the invention has been achieved by the following aspects of the invention.
(1) A microfilter cartridge wherein a microporous filter membrane, membrane supports, a core, an outer cover and end-plates constituting the filter cartridge are all made of a polysulfone polymer.
(2) The microfilter cartridge as described in (1), wherein the polysulfone polymer is polyether sulfone.
(3) The microfilter cartridge as described in (1), wherein the membrane supports are microporous membranes provided with a number of fine grooves and/or projections.
(4) The microfilter cartridge as described in (3), wherein the microporous filter membrane has a water bubble point of 0.3 MPa or more while the membrane supports have a water bubble point of 0.15 MPa or less.
(5) The microfilter cartridge as described in (1), wherein the membrane supports are polysulfone polymer films having been physically perforated and provided with a number of fine grooves and/or projections.
(6) The microfilter cartridge as described in (1), wherein the membrane supports are polysulfone polymer films provided with a number of fine grooves and/or projections and these fine grooves form together continuous fine grooves.
(7) The microfilter cartridge as described in (1), wherein the membrane supports are made of a net formed by knitting polysulfone monofilaments having a diameter of from 50 to 300 xcexcm.